311105040-计算机网络(B闭)

1/5311105040计算机网络（B闭）2015-2016-1一、单项选择题（本大题共20小题，每小题1.5分，共30分）。提示：在每小题列出的四个备选项中只有一个是符合题目要求的，请将其代码填写在下表中。错选、多选或未选均无分。1．WhichofthefollowingprotocollayersisnotexplicitlypartoftheInternetprotocolstack?A.applicationlayerB.sessionlayerC.datalinklayerD.Transportlayer2．IntheInternetprotocolstack,2-PDUiscalled:A.messageB.segmentC.datagramD.frame3．Amongthefollowingapplications,whichoneisnotsuitableforP2Parchitecture:A.filesharingB.electronicbankingC.videostreamingD.instantmessage4．Whichofthefollowingnodesbelongstothenetworkcore?A.awebserverB.ahostwithWin2008ServerC.arouterwithoutNATserviceD.asupernodeonSkypeNetwork5．AuserrequestsaWebpagethatconsistsofsometextand2images.Thebrowser’scacheisempty.Forthispage,theclient’sbrowser:A.sends1httprequestmessageandreceives1httpresponsemessages.B.sends1httprequestmessageandreceives2httpresponsemessages.C.sends2httprequestmessageandreceives3httpresponsemessages.D.sends3httprequestmessageandreceives3httpresponsemessages.6．CookiesenableA.aWebservertoinfectauser’smachinewithmalwareB.aWebservertotrackauser’sactivityatitsownWebsiteC.aWebservertoknowallpreviousWebpagesvisitedbytheuserD.aWebservertolearnauser’spersonalinformation.7．Whenauserretrieveshisemailfrommailserver,whichoffollowingprotocolscan’tbeused?A.POP3B.HTTPC.SMTPD.IMAP8．IntheCSMA/CDprotocol,whatconditiononthetransmissiondelaytransTandthepropagationdelaypropThastobesatisfiedtoguaranteethatanodealwaysdetectsacollision?A.transpropTTB.2transpropTTC.transpropTTD.2transpropTT9．Twohostssimultaneouslysenddatathroughalinkofcapacity1Mbps.HostAgeneratesdatawitharateof1MbpsandusesTCP.HostBusesUDPandtransmitsa100bytespacketevery1ms.Whichhostwillobtainhigherthroughput?2/5311105040计算机网络（B闭）2015-2016-1A.HostA.B.HostBC.Theyobtainroughlythesamethroughput.D.Theyexperiencecongestioncollapseandnegligiblethroughput.10．Innetwork-assistedcongestioncontrol,whichthestatementsbelowiscorrect?A.Endsystemsdetectcongestionsonlybasedonobservedcongestioninthenetwork.B.EndsystemsusetheATMprotocoltodetectcongestions.C.Network-layercomponentsprovideexplicitfeedbacktothesenderregardingthecongestionstateinthenetwork.D.Noneoftheabove.11．InTCP,thetimeoutintervalisafunctionof:A.estimatedRTTatthesenderB.MSSandtheoverheadofasegmentC.thesizeofbufferatthereceiverD.thesizeofsendingwindow12．SupposehostAsendshostBoneTCPsegmentwithsequencenumber418,acknowledgementnumber571,and4bytesofdata.Thenthesequencenumberintheacknowledgementtothissegmentis_________A.422B.418C.571D.57513．Whichofthefollowingnetworkdeviceactsonbits?_________A.HUBB.SwitchC.RouterD.Bridge14．Let’sassumethereis16-bitpiecedata1011101110011001,The8-bitInternetchecksumforthisdatashouldbe_________A.01010100B.01010101C.10101011D.1010101015．Forthedatainthelastquestion(14),theCRCisappliedtoitwithgenerator1001.ThustheCRCbitsshouldbe_________A.010B.001C.111D.10116．Considerarouterwiththeswitchingfabricbasedonsharingmemory.Thememoryaccessspeed(readandwrite)isBpacketspersecond.TheoverallforwardingthroughputisalwaysA.greaterthanBpacketspersecondB.greaterthanB/2packetspersecondC.lessthanB/2packetspersecondD.lessthan/2Bpacketspersecond17．InanEthernetframe,thepreambleisresponsibleforA.collisiondetectionB.errordetectionC.synchronizationofthereceiver’sclocktothesender’sclock.D.multiplexing/demultiplexing18．WhichofthefollowingservicesisnotprovidedbyDNS?_________A.hostaliasingB.mailserveraliasingC.loaddistributionD.IPaddressallocating3/5311105040计算机网络（B闭）2015-2016-119．Giventhattherequestedinformationisnotavailableatanyintermediatedatabases,apurelyrecursiveDNSqueryfromarequestinghostwouldfollowthepath:A.Rootnameserver;TLDnameserver;localnameserver;authoritativenameserver.B.authoritativenameserver;TLDnameserver;Rootnameserver;localnameserverC.TLDnameserver;Rootnameserver;localnameserver;authoritativenameserver;D.localnameserver;Rootnameserver;TLDnameserver;authoritativenameserver;20．DuringnormalIPpacketforwardingatarouter,whichthefollowingpacketfieldwillbeupdated?A.ChecksumB.SourceIPC.DestinationIPD.Typeofservice二、判断并说明理由（本大题共10小题，每小题2分，共20分）。提示：正确打，错误打，将其结果填写在下表中，对于错误的，请指出理由。1．Allbiterrorscanbedetectedifapacketissenttwice.2．TheefficiencyofunslottedALOHAistwicethatofslottedALOHA3．Wirelessnetworkscanperformcollisiondetection4．Asalinkstatealgorithm,RIPplaysanimportantroleinLAN5．IPv6routerswillbefasterthanIPv4routers6．OSPFisnewerandhasmoreflexibilityandoptionsthanRIP7．Awebcacheisbothaserverandclient.8．ThesequencenumberrangemustbeatleasttwicethesendwindowforGBN9．Poisonedreversecanavoidthe“counttoinfinity”problemtotally10．UDPareTCParethesameforapplicationsthatsendonepacketatatime三、简答题（本大题共4小题，共20分）。1．Onedayat3:00pmAliceaccessedthewebsite(5points)2．Westudiedanumberofmultipleaccessprotocolsinthiscourse,including(1)TDMA,(2)CSMA,(3)SlottedAlohaand(4)Tokenpassing.Supposeyouwerechargedwith4/5311105040计